With five weeks to go before Election Day, Democrats are still waiting for Donald Trump to create the nationwide swell that would be necessary to put the Republicans’ House majority into play. House races are often late to engage but, thus far, the developments have been a mixed bag for Democrats, keeping sizable gains out of reach.

The lack of vulnerable Democrats — and the resiliency of many Republican incumbents in the face of an unpopular presidential nominee — could amount to a historic election in the House, but not in the way one might think. The cycle could produce the fewest number of House seats to flip party control in 60 years.

The Congressional Leadership Fund, a super PAC backed by House Republican leadership, is pouring another $10.7 million into House races as the GOP seeks to defend their hold on the lower chamber and flip several Democratic-held seats.

The additional spending brings the fund's general election expenditures this cycle to $20.7 million in 15 House districts, nearly twice what it spent in 2014 and 2012. The super PAC spent $11.6 million in 2014 and $10.7 million in 2012.

House Majority PAC, a super PAC that helps elect Democrats to the House, placed additional TV reservations Monday that bring its total early ad buys to more than $19.6 million across 23 media markets for the final weeks of the 2016 campaign.

The new reservations include $214,000 in Marquette, Michigan, and $378,000 in Traverse City, Michigan.

Democrats have two competitive candidates in Iowa's 3rd district — a seat the party needs to win to make gains in the House this year — and competing polls released from both candidates Thursday show the race remains tight.